Marrow nails are used in tubular bones in humans and animals for healing fractures or for facilitating bone elongation. In marrow nails known in the prior art, the nails are secured in the bone by screws which must be guided through bore holes provided in the marrow nail. In these known marrow nails, an elongated hole is provided at the opposite, proximal end of each of the nails which elongated hole may be used in cooperation with a hook for outward movement or deflection of the nail. However, such marrow nails have several disadvantages. For example, problems are caused on the one hand by the necessity of guiding the screws through the bore holes in the nail. This arrangement renders it difficult to secure the screws to the marrow nail. In addition, the connection of the marrow nail with the hook is cumbersome and inconvenient.